Tan
I believe the "Emergency Purge Mode Switch" works well for fumes, vapors, and some light mists, not so much for flammables that are combusting. The instruction manual/instructions/vendor/installer should have mentioned this. To put out active fire in a hood or the ductwork, a built-in Fire Suppression system needs to be installed. The purge fan only increases the air flow - which you have discovered.
More responses from the rest of the list to follow, I'm sure.
Bill Parks
CHST, CHMP, CEHT, CIE(pending), LSP(C), RPIH
630/380-4032
**Providing sound Industrial Hygiene, Occupational Safety and Health, Environmental Health & IAQ, Environmental, and Laboratory support services and solutions for over 25 years**
--- On Fri, 3/5/10, Tan Khai Seng wrote:
> From: Tan Khai Seng
> Subject: [DCHAS-L] Emergency purge mode for fumehood
> To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
> Date: Friday, March 5, 2010, 10:36 AM
> Hi everyone
>
> for some fumehood, especially the VAV fumehoods, they come
> with an emergency purge button which is supposed to increase
> the exhaust rate in the event of a spillage.
>
> I have just encounter an incident where a distillation was
> wrongly set up, the set up went flying after 2 hours and
> toluene was spead all over the fumehood. The researcher
> instinctively close the sash fully and activate the
> emergency purge mode. by then, the toluene had ignited and
> the activation of the purge mode actually fanned the fire.
> the fire was big enough to melt the flexible duct connecting
> the fumehood to the exhaust duct. the researcher was able to
> contain the fire within the fumehood and extinguish it with
> the fire extinguisher.
>
> we are debating over the question of whether to activate or
> not to activate the emergency purge button.
>
>
>
> any advise?
>

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